A conventional system or device for displaying an image, such as a display, projector, or other digital imaging system, is frequently used to display a still or video image on a display surface, such as a display screen. Viewers evaluate display systems based on many criteria such as image size, color gamut, contrast ratio, brightness and resolution, for example. Image brightness, pixel color accuracy, and resolution are particularly important metrics in many display markets because the available brightness, color gamut and resolution can limit the size of a displayed image and control how well the image can be seen in venues having high levels of ambient light.
Many digital display systems create a full color display with a single light modulator by creating three or more modulated images in primary colors (red, green, and blue) per video frame. The primary colors are typically derived by passing a white light through a color wheel, prism, or some other color filter before causing the light to impinge the modulator. Sometimes, the white light is passed through a spatial light homogenizer after the color wheel to even out the intensity of the white light. The modulated images are sequentially displayed at a high rate so as to create a full color image in the human visual system. Thus, this method of generating a full color display is called “sequential color.” Although the use of sequential color yields the desired red, green, and blue light for image formation, it does so by blocking the transmission of undesired light wavelengths. In other words, a significant portion of the light emitted by the light source is wasted, resulting in a decreased brightness of the final displayed image.
Color wheels add noise, thickness, expense, and complexity to a display system for a variety of reasons, including the inherent long-term reliability problems associated with moving mechanical parts. Further, approximately two-thirds (⅔) of the white light is wasted when using a color wheel because two out of the three colors (in a three-color scheme) are reflected by the color wheel at any given time. The embodiments described herein were developed in light of these and other drawbacks associated with known display systems.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.